The invention relates to an apparatus for pulmonary function analysis, in particular, for measurement of functional respiratory volumes, or respiratory capacities, respectively, comprising a respiratory bag which can be connected to the examination subject via a first valve system by means of a respiratory tube, and which can be connected to a test gas receptacle via an additional valve system, or the like, and comprising a gas analysis device for measurement of the test gas concentration in the respiratory bag.
In order to determine functional respiratory volumes and/or respiratory capacities, for example, nitrogen washouts of the lungs are being carried out up to the present time. To this end, volume measurements, for example, with a spirometer, on the one hand, and concentration measurements of the respiratory gas, on the other hand, are necessary. An apparatus for carrying out such nitrogen-washouts is already prior knowledge, in which the volume measurement is simplified and only a precise nitrogen concentration measurement need still be carried out. This concentration measurement, subsequent to washout of the nitrogen, proceeds discontinuously therein on the part of partial specimens, removed from the respiratory bag, by means of chemical methods.
In addition to the special nitrogen-washouts of the lungs, for the same measuring purpose, wash-ins of defined test gas quantities, preferably inert gases, into the lungs are also known. Measured quantities are here essentially the initial- and end-concentration of the test gas. Thus, again, as precise as possible a concentration measurement is desired for which purpose corresponding gas analysis devices are necessary. In the known apparatus the concentration measurement proceeds by means of determination of the thermal conductivity which determination is, however, rather imprecise in the case of utilization of inert gases, so that the pulmonary function analysis remains unsatisfactory.